MANILA — The president’s office on Monday called Chinese seizures of fish caught by Philippine fishing boats near a disputed shoal unacceptable and presented three fishermen who described their experiences.

Presidential spokesman Harry Roque said he and Foreign Secretary Alan Peter Cayetano raised the incidents with the Chinese ambassador in Manila, who assured them that Chinese coast guard personnel would be punished if an investigation finds the accusations are accurate.

The incidents at Scarborough Shoal have sparked new criticism after a TV network interviewed fishermen and broadcast a video of the alleged confiscations. China has sparked alarm with its recent actions to fortify its sweeping territorial claims in the South China Sea, including the reported installation of anti-ship and anti-aircraft missiles on its newly built islands.

The incidents have increased pressure on President Rodrigo Duterte’s government to take a stronger stance toward China’s behavior in the disputed waters. Since his inauguration, Duterte has forged closer ties with China and avoided criticizing it in public.

Dozens of Filipino fishermen and left-wing activists protested at the Chinese Consulate on Monday.

“What they did to our fishermen ... shows that they have claimed the area and not only that they stole the fishermen’s catch that was supposed to feed their families on that day, their family went hungry because of this,” protest leader Roberto Aleroza said.

Roque said the government has taken action to prevent a repeat of the Chinese actions. “The Chinese coast guard should not be taking even a kilo and we’re not allowing this,” he said, adding that Duterte and Chinese President Xi Jinping have agreed that Filipinos should be able to fish freely at Scarborough.